title: SVR4 (suppressor of variegation 4) and SVR4-like: two proteins with a role in proper organization of the chloroplast genetic machinery.
abstract: SUPPRESSOR OF VARIEGATION 4 (SVR4, also called MRL7) and its homolog SVR4-like (also called MRL7-Like) were originally identified as important proteins for proper function of the chloroplast in Arabidopsis. Both are nuclear-encoded chloroplast-located proteins, and knockout mutants of either gene result in seedling lethality. Transmission electron microscopy analysis revealed that chloroplast development is arrested at an early developmental stage in both mutants. Accordingly, in the mutant plants severely decreased levels of photosynthetic pigments as well as subunits of the photosynthetic complexes could be detected. In absence of either of the two proteins chloroplast DNA organization was clearly affected. Immunological analysis revealed that SVR4 is a component of the transcriptionally active chromosome (TAC) from barley chloroplasts. Analyses of gene expression indicate that SVR4 and SVR4-like are required for proper function of the plastid transcriptional machinery. We propose that SVR4 and SVR4-like function as molecular chaperones ensuring proper organization of the nucleoids in chloroplasts.
authors.affiliation: Villum Centre of Excellence "Plant Plasticity" and Center for Synthetic Biology, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, DK-1871, Frederiksberg C, Denmark.
authors.forename: Marta
authors.initials: M
authors.lastname: Powikrowska
authors.forename: Anastassia
authors.initials: A
authors.lastname: Khrouchtchova
authors.forename: Helle Juel
authors.initials: HJ
authors.lastname: Martens
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Zygadlo-Nielsen
authors.forename: Joanna
authors.initials: J
authors.lastname: Melonek
authors.forename: Alexander
authors.initials: A
authors.lastname: Schulz
authors.forename: Karin
authors.initials: K
authors.lastname: Krupinska
authors.forename: Steven
authors.initials: S
authors.lastname: Rodermel
authors.forename: Poul Erik
authors.initials: PE
authors.lastname: Jensen
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D060365:Chloroplast Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D015536:Down-Regulation; D018506:Gene Expression Regulation, Plant; D001467:Hordeum / Q000235:genetics / Q000378:metabolism; D015151:Immunoblotting; D046529:Microscopy, Electron, Transmission; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D010788:Photosynthesis / Q000235:genetics; D030821:Plants, Genetically Modified; D036226:Seedlings / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013879:Thioredoxins / Q000235:genetics / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism; D019207:beta Carotene / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C000592338:At2g31840 protein, Arabidopsis; C000589129:At4g28590 protein, Arabidopsis; D060365:Chloroplast Proteins; D018832:Molecular Chaperones; D019207:beta Carotene; D002734:Chlorophyll; D013879:Thioredoxins; D012321:DNA-Directed RNA Polymerases